Various types of electrical stimulation have been known to be used for various therapeutic purposes. For example, one modality that has gained significant popularity is transcutaneous electrical nerve stimulation (TENS). TENS stimulates the generation of a current that flows through leads to electrodes that are placed on specific locations on a patient's skin in order to elicit reactions in sensory and motor nerve fibers, typically to block pain messages along the nerve fibers. As is known, TENS generally employs low-voltage current that is modulated at low frequency (i.e., 125 Hz) in order to elicit the desired response in the nerve fibers directly under the electrodes through which the current flows.
While TENS has proved successful in limited applications (i.e., involving the stimulation of nerve fibers located just under the skin), there are problems associated with using TENS and like modalities in various situations, which has limited the applications in which such electrical stimulating modalities have traditionally been used.
Specifically, it has been found that the lower the stimulation frequency of an electrical current, the greater the resistance to the passage of the current through the skin and other body tissues, leading to potentially significant discomfort being experienced by the patient. The skin's impedance at 50 Hz is approximately 3200 ohms, while at 4000 Hz it is reduced to approximately 40 ohms. The result of applying this latter frequency is that it will pass more easily through the skin and any other tissues before hitting the target tissue or organ. However, it has also been found that medium frequency current (e.g., 4000 Hz) generally does not have the beneficial therapeutic effects as does the much lower frequency currents typically employed by traditional modalities, such as TENS (e.g., 125 Hz).
Interferential current (IFC therapy) is a unique and separate form of electrical therapeutic stimulation that expands the scope and capabilities for medical intervention in situations not amenable to TENS or any other form of electrical therapy. In general, IFC therapy utilizes two or more medium frequency currents which pass through body tissues simultaneously. They are set up so that their paths cross; and in simple terms they interfere with each other (hence the name “interferential” current therapy). This interference gives rise to an interference or beat frequency, which has the characteristics of low-frequency stimulation. The exact frequency of the resultant beat frequency can be controlled by the input frequencies. For example, if one current is at about 4000 Hz and the other current is at about 3900 Hz, the resultant beat frequency would be at about 100 Hz.
Thus, the basic principle of IFC therapy is to utilize the strong physiological effects of the low frequency electrical stimulation of muscle and nerve tissues at sufficient depth, without the associated painful and somewhat unpleasant side effects of such low frequency stimulation. The medium frequency currents penetrate the tissues with very little resistance, whereas the resulting interference current (low frequency) is in the range that allows effective stimulation of the biological tissues. The resistance (impedance) of the skin is inversely proportional to the frequency of the stimulating current. Thus, the therapeutic beat frequency of IFC results in the desired physiologic response from the target organ or tissue, while requiring less electrical energy input to the deeper tissues than would be required if a single low frequency current was employed, giving rise to less discomfort.
However, the use of IFC is not without its problems. As discussed previously, when using TENS or the like low frequency therapies to treat relatively superficial nerves/tissues, correct placement of the electrodes immediately over the area to be treated is a relatively simple matter. However, being that the use of IFC allows for substantially deeper areas to be treated, and also being that IFC requires that multiple medium frequency currents intersect at the precise area to be stimulated (referred to herein as the “therapeutic target area”), targeting of the anatomic area to be affected becomes a required component of the use of IFC treatment, rather than simply putting electrodes on the skin to treat a localized area of pain and discomfort. Heretofore, there is no known system employing IFC which also adequately ensures that the stimulating currents are appropriately targeted such that they intersect to generate the correct beat frequency precisely at the therapeutic target area.
Therefore, what is desired is a system and method employing electrical stimulation for therapeutic purposes, which allows for deep penetration of an appropriate low frequency current but without causing tissue damage and/or patient discomfort and which ensures that the therapeutic low frequency currents are accurately directed to the desired therapeutic target area.